Field of the Invention
The present invention relates to a scanning optical apparatus provided in an image forming apparatus, such as a copying machine, printer, and facsimile machine, which forms an image on a recording medium, such as a sheet.
Description of the Related Art
A laser printer based on an electrophotographic recording method is provided with a scanning optical apparatus which scans a photosensitive body with laser light corresponding to image information. A configuration using a rotating polygon mirror is most commonly used as a deflector for deflecting laser light.
Known configurations of a motor portion for causing the rotating polygonal mirror to rotate include: a fixed-shaft-type motor (sleeve rotation type) in which a rotor turns about a fixed shaft, and a rotating-shaft-type motor in which the rotor is fixed to a rotating shaft. Since the polygon rotating mirror is fixed to the rotor, then when a fixed-shaft-type motor is used, the polygon rotating mirror rotates about the shaft. On the other hand, when a rotating-shaft-type motor is used, the rotating polygon mirror rotates with the shaft. In general, a fixed-shaft-type motor has higher rotational accuracy than a rotating-shaft-type motor. The type of motor to be used may also be decided depending on the performance required of the printer.
A deflector having a rotating polygon mirror is fixed to an optical box, which is a housing of a scanning optical apparatus. In the case of a deflector which uses a fixed-shaft-type motor, the shaft is fitted into and fixed to holes in the optical box. In the case of a deflector which uses a rotating-shaft-type motor, bearings which rotatably hold the shaft are fitted into and fixed to holes in the optical box. Since the diameter of the shaft and the diameter of the bearings are different, then when employing a deflector which uses a fixed-shaft-type motor, it is necessary to design an optical box having small fitting holes, and when employing a deflector which uses a rotating-shaft-type motor, it is necessary to design an optical box having large fitting holes.
In order to suppress costs relating to the printer, it has been envisaged that substantially the same scanning optical apparatus be employed in both a printer A and a printer B which has different characteristics to the printer A. However, in cases where it is necessary to employ a fixed-shaft deflector in the printer A and to employ a rotating-shaft deflector in the printer B, then it may be necessary to design separate optical boxes for the printer A and the printer B, and the effect in reducing costs is diminished.
In Japanese Patent Application Publication No. 2013-054082, a deflector is installed on a connection plate which can be fitted into an optical box. By installing a connection plate on which the deflector is installed, in the optical box, then deflectors of a plurality of types can be installed on an optical box of one type, via the connection plate.
However, in Japanese Patent Application Publication No. 2013-054082, a connection plate is required in order to install deflectors of a plurality of types in an optical box of one type, and the number of components in the scanning optical apparatus therefore rises, leading to an increase in the cost of the apparatus and the assembly steps involved in assembling the scanning optical apparatus.